Conventional prior art magnetic resonance imaging apparatus and techniques entail oblique imaging which permits image data to be taken from a plane through an object which is at an angle to one of the three orthogonal axes. Also, the prior art in this domain entails multi-slice imaging which permits image data, in one scan, to be taken in a plurality of parallel planes, through the object, which are orthogonal to one of the three orthogonal axes, which are uniformly spaced one from the other, and whose image centers are all aligned.
Further, present magnetic resonance imaging apparatus entail a combination of the above methods in an oblique multi-slice technique which was disclosed by FONAR Corporation in a technical exhibit at a conference of the Radiological Society of North America in November, 1984. Referring to FIG. 1, the oblique multi-slice technique permits images of an object 11, in one scan, to be obtained in planes, such as 1-7 extending into the paper, which are disposed at an angle P relative to one of the three primary orthogonal axes, arbitrarily designated Y. However, the planes 1-7 within a given scan are parallel, and have a constant distance D therebetween. Further, the positioning of the center of the image corresponding to the plane 1 determines the center of the image corresponding to each of the planes 2-7. That is, when the center of the image corresponding to the plane 1 is selected to be at a point 12 on the object 11, the centers of the images of the planes 2-7 are necessarily therefore at, respectively, points 13-18. The selection of the center of the image corresponding to the plane 1 at the point 12 determines the centers of the images corresponding to the other planes 2-7.
Accordingly, in the prior art, to generate an image from a first plane disposed at a first angle relative to one of the orthogonal axis, and to generate an image from a second plane disposed at a second angle, two scans are required. A full scan including the first plane disposed at the first angle must be taken, and then a second full scan including the second plane disposed at the second angle must be taken. Similarly, if the distance between planes is desired to be varied, then once again several scans are required, each having one of the desired distances between planes. Further, if the centers of the images corresponding to two or more planes are not desired to be aligned as in the prior art, then a separate scan is required to center the image of a particular plane. For example, to center the image corresponding to the plane 6 at the point 19 on the object 11, a second scan would be required; since, in the first scan the center of the image corresponding to the plane 6 coincides with the point 17.
Accordingly, to obtain images from planes which are not parallel to each other, or which possess varying distances between one another, or which have misaligned image centers, requires additional scans and time that is wasted in capturing nonessential information.
Thus, there is a need for an apparatus and method which permit, in a single scan, magnetic resonance images to be obtained from planes disposed at different angles, having varying distances therebetween, and having shifted image centers.